make a new kind of buffer where shrinking and adding in head can avoid

* include/libxml/tree.h tree.c: make a new kind of buffer where
  shrinking and adding in head can avoid reallocation or full
  buffer memmoves
* encoding.c xmlIO.c: use the new kind of buffers for output
  buffers
Daniel

svn path=/trunk/; revision=3787

1 files changed, 5 insertions, 3 deletions

diff --git a/include/libxml/tree.h b/include/libxml/tree.h
index 5afac525..6a6a09d9 100644
--- a/include/libxml/tree.h
+++ b/include/libxml/tree.h
@@ -71,9 +71,10 @@ typedef xmlEntity *xmlEntityPtr;
  */
 
 typedef enum {
-    XML_BUFFER_ALLOC_DOUBLEIT,
-    XML_BUFFER_ALLOC_EXACT,
-    XML_BUFFER_ALLOC_IMMUTABLE
+    XML_BUFFER_ALLOC_DOUBLEIT,	/* double each time one need to grow */
+    XML_BUFFER_ALLOC_EXACT,	/* grow only to the minimal size */
+    XML_BUFFER_ALLOC_IMMUTABLE, /* immutable buffer */
+    XML_BUFFER_ALLOC_IO		/* special allocation scheme used for I/O */
 } xmlBufferAllocationScheme;
 
 /**
@@ -88,6 +89,7 @@ struct _xmlBuffer {
     unsigned int use;		/* The buffer size used */
     unsigned int size;		/* The buffer size */
     xmlBufferAllocationScheme alloc; /* The realloc method */
+    xmlChar *contentIO;		/* in IO mode we may have a different base */
 };
 
 /**